This would make sense if every memory corruption vulnerability was equivalently exploitable, which is of course not true. I think you'll find Google does in fact fuzz ffmpeg, though.
At any rate, Google didn't employ "AI" to find this vulnerability, and Google fuzzing probably wouldn't have outcompeted these researchers for this particular bug (totally different methods of bugfinding), so it's really hard to find a coherent point you'd be making about "fuzzers", "AI", and "Google" here.